Oligomerizing alpha-olefins with a heterogeneous catalyst

ABSTRACT

An alpha-olefin is oligomerized in the presence of a three-component catalyst comprising a particulate solid adsorbent having boron trifluoride and water adsorbed on the solid adsorbent. For example, 1-decene is oligomerized to a product predominating in the trimer and tetramer using silica as the solid adsorbent.

SUMMARY OF THE INVENTION

An alpha-olefin is oligomerized in the presence of a three-componentcatalyst comprising boron trifluoride, a minute amount of water and aparticulate adsorbent material such as silica to a product predominatingin those oligomer fractions having viscosities within the lubricatingoil range such as the trimer and tetramer of 1-decene.

DESCRIPTION OF THE INVENTION

The oligomer mixtures produced from certain 1-olefins, that have beenpolymerized using boron trifluoride as the catalyst, have been useful asbase fluids for preparing lubricants, hydraulic fluids, transmissionfluids, transformer fluids and the like, generically designated by theterm functional fluids. The oligomer products of 1-olefins having fromfour to 12 carbon atoms or mixtures of these have been described asuseful for preparing these functional fluids with the oligomer productof 1-decene being particularly preferred in current usage. Thefunctional fluids that have been prepared from 1-decene for use in motoroils contain various proportions of the trimer, tetramer and pentamerfractions, the dimer having been removed because it possessessignificant volatility and low viscosity. However, even this 20-carbonoligomer can be useful as a functional fluid in specific applications.

In the oligomerization reaction, the use of a promoter or co-catalystwith the boron trifluoride has been conventional in order to obtainuseful catalytic activity for the boron trifluoride. The co-catalystcomplexes with the boron trifluoride to form a coordination compoundwhich is catalytically active for the oligomerization reaction. Includedin the list of substances which have been recommended as co-catalystsare various polar compounds including aliphatic ethers, such as dimethylether and diethyl ether; aliphatic alcohols, such as methanol, ethanol,n-butanol and decanol; polyols, such as ethylene glycol and glycerol;water; aliphatic carboxylic acids, such as acetic acid, propanoic acidand butyric acid; esters, such as ethyl acetate and methyl propionate;ketones, such as acetone; aldehydes, such as acetaldehyde andbenzaldehyde and acid anhydrides, such as acetic acid anhydride andsuccinic anhydride. The use of these boron trifluoride coordinationcompounds is described in U.S. Pat. Nos. 3,149,178; 3,382,291;3,742,082; 3,763,244; 3,769,363; 3,780,128; 3,997,621; 4,045,507 andothers.

Although these coordination compounds of boron trifluoride are veryeffective oligomerization catalysts for the higher alpha-olefins,experiments have demonstrated that they possess a significantly reducedactivity when they are reused in the oligomerization reactor afterrecovery from the product stream. Therefore, this inability to reuse thecatalyst requires the substantial continuing expense of fresh catalystand co-catalyst. There are also presented the additional problems notonly of a substantial cost of waste treatment and disposal proceduresfor the spent catalyst but also the possibility of environmentalcontamination, all of which can make the process prohibitive.

We have discovered a process for the oligomerization of 1-olefins whichutilizes a three-component catalyst system comprising a particulatesolid adsorbent, water and boron trifluoride. In our process the borontrifluoride can be readily recovered from the oligomer product for reusein the oligomerization reactor at its original activity without thesignificant loss in activity as is experienced with the polar compoundcomplexes of boron trifluoride. As a result, catalyst and wastetreatment costs are minimized and disposal and environmental problemsare substantially avoided. Furthermore, the use of our catalyst systemunder appropriate reaction conditions results in a high conversion ofthe 1-olefin to the desired oligomer fractions.

A particulate solid adsorbent is utilized in the oligomerization reactoras one of the components comprising our three-component catalyst system.This solid adsorbent can be positioned in the reactor as a bed forflow-through contact with the reaction liquid or it can be maintained asa slurry in the reaction liquid by suitable agitation in a batch orcontinuous reaction. When the reaction vessel is pressured with borontrifluoride, the second component of our catalyst system, a substantialquantity of the boron trifluoride is adsorbed by the solid adsorbent toform an active oligomerization catalyst. Since boron trifluoride readilydesorbs from the solid adsorbent, a suitable boron trifluoride pressureand a suitable concentration of boron trifluoride in the reaction liquidis maintained during the oligomerization reaction to insure that thecatalytically active solid adsorbent-boron trifluoride combination ismaintained throughout the course of the oligomerization reaction.

However, we have observed that this two-component catalyst comprisingthe solid adsorbent and the boron trifluoride gradually loses activityafter a period of continued use, which aging cannot be convenientlycorrected by increasing the boron trifluoride pressure. We believe thatthis catalyst aging is the result of gradual physical and chemicalchanges in the solid adsorbent-boron trifluoride catalyst as it is beingused. Unexpectedly, we have discovered that this aging can essentiallybe prevented if a minute amount of water is fed to the reactor in the1-olefin feed. This water is also adsorbed by the solid adsorbent toform the three-component catalyst system of our invention. Not only doesthis three-component catalyst system prevent aging of the catalyst, butsurprisingly, we have further discovered that a solid adsorbent-borontrifluoride catalyst which has aged in an absence of water in thereaction feed can be regenerated to substantially its original activitymerely by introducing the requisite amount of water with the feed olefinand continuing the reaction.

We have further discovered that the overall conversion of the 1-olefinis significantly improved without substantial change in the selectivityto the various oligomer fractions by the presence of our three-componentcatalyst is comparison with the water-free catalyst. As a result of thisgreater catalyst activity resulting from the use of water, the processcan be operated at a greater throughput of the 1-olefin feed asdetermined by the liquid hourly space velocity. Another benefit in thisgreater catalyst activity is that the process can be operated with lessboron trifluoride in the catalyst and therefore less boron trifluoridefed to the reactor.

We have determined that the beneficial results that are obtained in ourprocess by the use of water in association with the solid adsorbent andboron trifluoride catalyst components are obtained within the solubilitylimits of the water in the 1-olefin. For example, we have found that theupper solubility limit of water in 1-decene is from 100 to 130 ppm.(parts by weight of water per million parts by weight of 1-decene) at25° C. In general, an upper limit of 40 to 50 ppm. water in the olefinfeed is all that is generally necessary to obtain the full benefits ofthe three-component catalyst system in the oligomerization reaction. Aminimum amount of water is necessary in order for its use to beadvantageous. For example, although improvement in conversion and in themantenance of catalyst activity can be observed when the 1-olefin feedcontains about five ppm. water it is preferred that the feed olefincontain at least about ten ppm. water for significant improvement and atleast 20 or 25 ppm. water is desired for substantial improvement inconversion and maintenance of catalyst activity.

As is the case with the prior art oligomerizations, 1-decene is the mostpreferred alpha-olefin for preparing synthetic lubricants and relatedfunctional fluids by our novel process. However, 1-olefins having fromthree to 12 carbon atoms and preferably eight to 12 carbon atoms orvarious combinations of these alpha-olefins can also be used. Thestraight chain olefins, generally referred to as the normal 1-olefins,are preferred, however branched chain 1-olefins can comprise a portionor all of the 1-olefin feed. A potentially significant result in varyingthe molecular structure of the 1-olefin is an effect on the propertiesof the resulting oligomer, including the viscosity, pour point andvolatility, and it is for this reason that the straight chain 1-olefinsare preferred. When a 3- or 4-carbon olefin is used, it is generallypreferred that this lower olefin be co-oligomerized with at least about20 mol percent of one or more of the higher olefins in order to obtainthe desired oligomer mixture.

In its broadest aspect, the lubricating oil range to which our processis directed varies between about 20 to about 50 carbon atoms, and moreparticularly between about 24 and 42 carbon atoms, and most preferablyabout 30 to about 40 carbon atoms. Our process is therefore preferablycarried out under appropriate conditions to obtain the maximum oligomerselectivity within the desired range of carbon numbers. One of theparticular benefits of our three-component catalyst system is that highproduct selectivity within the lubricating oil range is readily obtainedand under appropriate conditions the selectivity is even enhanced. Sinceit is difficult to separate or even determine by analysis the differentoligomer fractions having about 50 carbon atoms and higher, referenceherein to an oligomer fraction having about 50 carbon atoms is intendedto include the possible presence of minor amounts of one or moreoligomer fractions having a higher number of carbon atoms.

Any solid adsorbent material, inorganic or organic, which has a surfacearea of at least about 0.1 m² /g. and which is insoluble in the reactionliquid can be used as the solid adsorbent in our process. The class ofinorganic adsorbents include silica, the silica-aluminas,silica-zirconia, silica-magnesia, silica-thoria, alumina, magnesia,zirconia, activated carbon, the zeolites, silicon carbide, siliconnitride, titania, aluminum-aluminum phosphate, zirconium phosphate,thoria, the magnesia-aluminas such as magnesium aluminate, zincaluminate, pumice, naturally occurring clays, such as diatomaceousearth, and the like. The class of organic adsorbents includes porourpolyvinyl alcohol beads, porous polyethylene glycol beads, themacroreticular acid cation exchange resins, such as the sulfonatedstyrene-divinylbenzene copolymer exchange resins (for example,Amberlyst-15 and Amberlite-XN1040 supplied by Rohm and Haas Company,Philadelphia, Pa.), and the like. We prefer silica or a compositioncomprising at least about 50 percent silica as the solid adsorbent.

The three-component catalyst is preferably used as a fixed bed ofrelatively uniformly sized particles in a flow-through reactor. We havedetermined that the external surface area of the catalyst is a moresignificant factor with regard to catalyst activity than its porevolume. As a result, the particle size can be of particularsignificance. In general, the smaller the particle size the greater theactivity at constant catalyst volume, however, a catalyst bed formedfrom too finely sized particles tends to restrict the flow of thereaction stream as indicated by a significant pressure drop across thecatalyst bed. For these reasons the particle size of the catalyst ispreferably at least about 100 mesh (0.15 mm.) in particle size, and mostpreferably at least about 50 mesh (0.3 mm.). The maximum particle sizeis preferably about 3 mesh (6.7 mm.) and most preferably about 10 mesh(2.0 mm.). However, useful oligomer products can be prepared with solidadsorbent outside these limits of particle size. When a slurry of thethree-component catalyst is used in a reactor, not only the particlesize but also the amount of the catalyst exerts a significant effect onthe rate of reaction.

The reaction temperature also exerts a significant effect on thereaction. As the temperature increases at constant contact time, boththe conversion and the selectivity to oligomers higher than the dimerdecreases while the amount of the dimer increases. For this reason it isdesirable that the maximum reaction temperature be about 150° C.,preferably no higher than about 100° C. and most preferably no higherthan about 50° C. On the other hand although the reaction can be carriedout at a temperature as low as about -50° C., it is preferred that theminimum operating temperature be at least about -10° C. We believe thatthe temperature affects the solubility of the boron trifluoride in thereaction liquid and also affects the adsorption of both the water andthe boron trifluoride on the solid adsorbent and that these cumulativeeffects help to cause the inverse relationship of temperature withconversion. We have found, in general, that a temperature gradientexists across the catalyst bed during the reaction by as much as 10° C.or more. The term reaction temperature therefore refers to the highesttemperature or "hot spot" temperature in the catalyst bed. On the otherhand a uniform temperature will be present in a slurry reactor.

Desirably the boron trifluoride gas and the 1-olefin are either jointlyintroduced into the inlet end of the reactor or alternatively the borontrifluoride can be injected into the 1-olefin feed stream immediatelyprior to its introduction into the reactor. This procedure is followedto essentially eliminate any direct reaction in the olefin feed line ofthe boron trifluoride with the water dissolved in the olefin and/oravoid undesired and uncontrolled oligomerization in the olefin feed lineprior to the reactor itself. Furthermore, this procedure permits theboron trifluoride and the water to be adsorbed by the solid particulatematerial within the reactor to form the three-component catalyst systemin the desired manner.

Since boron trifluoride continuously desorbs from the solid adsorbentduring the course of the reaction, it is necessary to feed borontrifluoride to the reaction inlet to insure that sufficient borontrifluoride is present in the catalyst for the oligomerization reaction.The adsorption and desorption of the boron trifluoride is affected bymany operating variables including temperature, pressure, moisturecontent, nature and particle size of the solid adsorbent, thecomposition of the feed and the reaction mixture, and the like. Theminimum feed rate of the boron trifluoride will therefore depend on theparticular operating conditions in any specific situation.

Typically, the boron trifluoride feed rate is at least equal to itssolubility in the reaction liquid at the particular conditions ofoperation, and preferably is in excess of its solubility in the reactionliquid. The solubility of the boron trifluoride in the reaction liquidis significantly affected by the partial pressure of boron trifluoridein the gas phase. We have also found that the boron trifluoride partialpressure exerts a significant effect on the amount of boron trifluorideadsorbed by the solid adsorbent and on the resulting catalyst activity.As a result, variations in pressure result in significant variations inconversion but with only moderate variations in product selectivity.Pure boron trifluoride gas can be utilized or it can be used inadmixture with an inert gas such as nitrogen, argon, helium, and thelike. When used as a mixture, it is preferred that it comprise at leastabout 10 mol percent of the gas mixture.

Because of the many variables involved, as indicated, it is difficult tospecify a feed rate for the boron trifluoride for any particular set ofoperating variables, although it can be stated that, in general, it willbe at least about 0.1 weight percent of the 1-olefin. It is moremeaningful to indirectly indicate the amount of boron trifluoride fed tothe reactor by specifying the partial pressure of boron trifluoride inthe reactor. Even though the oligomerization reaction can be carried outat atmospheric pressure when using pure boron trifluoride, we find itdesirable to maintain a partial pressure of boron trifluoride in thereactor of at least about 10 psig. (0.17 MPa) for suitable catalystactivity and preferably at least about 50 psig. (0.44 MPa) for superiorcatalyst activity. Partial pressures of boron trifluoride as high asabout 500 psig. (3.55 MPa) and higher, such as about 1,000 psig. (7.03MPa), can be utilized but it is preferred that an operating partialpressure of about 250 psig. (1.83 MPa) not be exceeded. The elevatedpressures are, in general, avoided where their possible benefits inimproved catalyst activity are outweighed by the added boron trifluorideand process costs. Lower operating pressures also appear to result in animproved product quality, possibly resulting from reduced isomerization.

When the fixed bed reactor is used, suitable results can be obtainedwith a relatively high throughput of the liquid reactant olefin. Infact, we find that conversion of the 1-olefin is only moderatelydecreased as the space velocity of the reactant liquid is increased. Inthe case of a 1-decene feed an increase in space velocity results in anincrease in the dimer and a corresponding decrease in the higheroligomer fractions. The oligomerization reaction in a fixed bed canconveniently be carried out within the broad range of liquid hourlyspace velocities, that is, the volume of the liquid feed per volume ofcatalyst per hour, of between about 0.1 and about 50 hr.⁻¹, butpreferably the reaction is carried out within the range of about 0.5 andabout 10 hr.⁻¹. These ranges for space velocity are also applicable witha flow-through slurried catalyst system.

Since the oligomerization reaction involves a series of competingreactions, monomer with monomer, monomer with dimer, dimer with dimer,monomer with trimer, etc., resulting in a series of product oligomerfractions, the particular reaction conditions utilized will depend onthe 1-olefin feed that is used and the product oligomer, fraction orfractions, that is desired. Although it is preferred that the reactionbe carried out at maximum conversion and optimum selectivity to desiredproducts, such may not be possible. However, the overall selectivity maybe substantially improved if those oligomer fractions lower than thedesired oligomer fractions are recovered from the product stream andrecycled to the feed stream for further reaction. Since the oligomerfractions which are heavier than the desired fractions represent aprocess loss, it may be desirable to operate the oligomerizationreaction under conditions which minimize the undesired heavier fractionseven though this may increase the amount of product recycle.

The expression reaction liquid as used herein refers to the alpha-olefinmonomer or mixture of monomers, any inert solvent, if present, and theoligomer products which will be present once reaction has started. It ispossible to carry out the reaction in the presence of up to about 80percent, preferably up to about 60 percent, of a suitable inert solvent.Suitable solvents can be used for temperature control and for productcontrol. Such solvents tend to slow down the various reaction rates andcan be utilized in conjunction with the different variables to controlthe course of the reaction and the nature of the reaction products.Suitable solvents can be selected from aliphatic hydrocarbons such aspentane, hexane, heptane, and the like; and aromatic hydrocarbons, suchas benzene, toluene, chlorobenzene, and the like. The solvent, ifutilized, should be liquid at reaction conditions and should besubstantially lower in boiling point than any other component tosimplify separation upon completion of the reaction.

In the slurried catalyst system, the three-component catalyst ismaintained as a slurry in the reaction liquid by suitable agitation. Inthe continuous slurry procedure, a suitable porous plate is positionedbetween the reaction liquid and the reactor outlet. A continuous streamof reaction product is removed at a rate to provide a predetermineddesirable average residence time in the reactor. Since the filter plateprevents the egress of the powdered adsorbent, the product stream isfree of solids. As the product is removed, make-up alpha-olefin isinjected into the reactor inlet to provide a constant liquid volume inthe reactor. The particle size of the adsorbent, the openings in thefilter plate and the vigor of the agitation are appropriatelyintercorrelated to insure that the adsorbent particles neither block thefilter openings nor cake up on the filter plate. The batch method can becarried out in the same equipment with the catalyst remaining in thereactor between batches or if a filter plate is not used, the slurry canbe removed from the reactor at the termination of a batch, filtered andthe catalyst returned for the next batch.

The reaction product which is removed from the reactor containsunreacted feed olefin, the various product oligomer fractions, anyimpurities which were originally present in the feed olefin, inertsolvent when used, and dissolved boron trifluoride gas. The amount ofboron trifluoride in the product liquid will, in general, fall withinthe range of between about 0.1 and about 20 weight percent dependingupon the amount of boron trifluoride that is fed to the reactor andusually in the lower end of this range. This boron trifluoride can bereadily separated from the liquid product in nearly quantitative yieldby subjecting the product solution to a vacuum at about 100° C., byheating the product light to 100° C. and bubbling nitrogen through theliquid, or by any other appropriate procedure. This separated borontrifluoride is reusable in the process without any change in theactivity of the three-component catalyst system. Traces of the borontrifluoride can be removed from the reaction product with a water wash.The liquid reaction product can then be hydrogenated to eliminate doublebond unsaturation either before or after its separation into the desiredfractions.

DESCRIPTION OF PREERRED EMBODIMENTS

The following experiments were carried out in a vertically mounted,stainless steel reactor one-half inch (12.7 mm.) in internal diameterand two feet (61 cm.) in length. A 20-inch (51 cm.) thermocouple wellwas positioned within the reactor to determine the temperature atdifferent locations within the catalyst bed. The 1-decene reactant waspumped into the bottom of the reactor and dry boron trifluoride wasinjected into the 1-decene feed line immediately before it entered intothe reactor. The product stream was collected in a 500 cc. receiver.

The 1-decene typically contained 1.5 percent saturates and otherolefins. The solid adsorbent was Davison Grade 59 silica having a B.E.T.area of about 250 m² /g, which was calcined at 1,000° F. (538° C.) andsized to the desired mesh size. The reactor was packed with 60 cc. ofthe silica and boron trifluoride gas was injected into the reactor andmaintained under pressure for 30 minutes before each series ofexperiments. Product analysis was carried out with a liquid or gaschromatograph as appropriate. The flow rate of the boron trifluoride gasin the following examples has been standardized to one atmospherepressure and a temperature of 60° F. (15.6° C.).

EXAMPLE 1

This example which utilized dry 1-decene and an excess of borontrifluoride demonstrated catalyst aging as evidenced by a substantialreduction in the percent conversion of the 1-decene feed over arelatively short period of time. The reactor contained 60 cc. of 40/50mesh (0.3 to 0.42 mm.) silica. The 1-decene was fed into the bottom ofthe reactor at a rate of 45 cubic centimeters (cc.) per hour (LHSV=0.75hr⁻¹) and the boron trifluoride was injected into the 1-decene feed lineat the rate of 11.4 cc. per minute, which was 6.15 weight percent borontrifluoride based on the 1-decene. The reactor was operated at an outletpressure of 250 psig. (1.83 MPa). After operating for three hours toinsure stable operation, analyses of the reaction products were begun.The temperature in the catalyst bed began to rise moderately in the 49thhour, which was believed to be the cause of a shift in the productselectivity. The results are set out in Table I.

                  TABLE I                                                         ______________________________________                                        Max.                                                                          Temp.                Selectivity                                              Hours °C.                                                                              Conv. %  C.sub.20, %                                                                           C.sub.30, %                                                                         C.sub.40, %                            ______________________________________                                         3    29        88.1     38.6    54.8  5.75                                   12    31        84.8     37.8    49.6  10.0                                   20    27        80.8     36.8    55.5  6.5                                    32    30        74.7     41.7    53.2  5.1                                    40    27        66.5     42.1    54.0  3.9                                    54    36        58.1     50.3    46.6  3.0                                    ______________________________________                                    

EXAMPLE 2

The experiment of the preceding example was continued in all detailsexcept that the feed of boron trifluoride was cut in half to 5.70 cc.per minute. However, after about four hours, the dry 1-decene wasreplaced with 1-decene which contained 28 ppm. water (the average of twoanalyzed samples). After conditions in the reactor stabilized, theconversion increased to its original value and stayed there for about 20additional hours as set out in Table II.

                  TABLE II                                                        ______________________________________                                        Max.                                                                          Temp.                Selectivity                                              Hours °C.                                                                              Conv. %  C.sub.20, %                                                                           C.sub.30, %                                                                         C.sub.40, %                            ______________________________________                                         1    36        57.8     48.4    47.8  3.7                                    10    28        80.6     45.0    48.4  6.6                                    16    27        83.0     44.5    51.2  3.8                                    22    27        87.7     42.1    52.8  5.1                                    30    27        88.2     39.2    49.7  9.1                                    ______________________________________                                    

EXAMPLE 3

In this experiment the reactor contained 60 cc. of a fresh batch of40/50 mesh (0.3 to 0.42 mm.) silica which had been pretreated with borontrifluoride under pressure. The 1-decene contained 42 ppm. water and wasfed to the reactor at a rate of 300 cc. per hour which is a liquidhourly space velocity of 5.0 hr⁻¹. Boron trifluoride gas was fed to the1-decene immediately prior to the reactor at a rate of 38.8 cc. perminute, which was 3.14 weight percent boron trifluoride based on the1-decene. The reactor outlet was operated at 150 psig. (1.14 MPa). Thehot spot temperature in the reactor rose for the first several hoursdropping after about eight hours to steady state operation. The resultsof 43 hours of operation are set out in Table III.

                  TABLE III                                                       ______________________________________                                        Max.                                                                          Temp.                Selectivity                                              Hours °C.                                                                              Conv. %  C.sub.20, %                                                                           C.sub.30, %                                                                         C.sub.40, %                            ______________________________________                                         7    52        87.8     19.7    53.4  18.9                                   19    18        87.9     21.4    65.0  13.1                                   27    27        88.1     22.8    62.6  11.5                                   35    20        89.2     23.9    62.1  12.8                                   43    21        90.6     22.8    61.8  13.7                                   ______________________________________                                    

EXAMPLE 4

A series of experiments were conducted to determine the effect ofreactor pressure on catalyst activity as determined by the conversion of1-decene and on product selectivity. A fresh 30 cc. batch of the 40/50mesh silica was placed in the reactor and was treated with borontrifluoride gas at 240 psig. (1.76 MPa) for 30 minutes. The 1-decene wasfed to the reactor at a rate of 150 cc. per hour (LHXV=5.0 hr⁻¹) and theboron trifluoride was fed at a rate of 19.38 cc. per minute (3.14 weightpercent). The results are set out in Table IV in which the pressure isthe outlet pressure and the temperature is the hot spot temperature inthe catalyst bed.

                  TABLE IV                                                        ______________________________________                                                          Selectivity                                                 Pressure,                                                                              Temp.,  H.sub.2 O                                                                            Conv. C.sub.20,                                                                            C.sub.30,                                                                          C.sub.40,                           psig. (MPa)                                                                            °C.                                                                            ppm.   %     %      %    %                                   ______________________________________                                        atm.     -2      24     24.7  32.8   59.4 6.9                                 50(0.44)  1      50     45.9  20.1   70.6 8.4                                 85(0.69)  20     40     87.8  17.7   64.0 15.3                                ______________________________________                                    

EXAMPLE 5

A further series of experiments was conducted to study the effect oftemperature on the catalyst activity and on product selectivity. A 30cc. charge of 20/30 mesh (0.59 to 0.84 mm.) silica which had beenpreviously treated with boron trifluoride gas under pressure was used inthese experiments. The 1-decene containing about 45 ppm. water was fedto the reactor at a rate of 90 cc. per hour (3.0 LHSV hr⁻¹) and theboron trifluoride gas was injected at a rate of about 12.0 cc. perminute (3.23 weight percent). The reactor was operated with an outletpressure of 125 psig. (0.965 MPa). The results are shown in Table V inwhich the temperature is the hottest temperature measured in thecatalyst bed.

                  TABLE V                                                         ______________________________________                                                      Selectivity                                                     Temp. °C.                                                                         Conv. %  C.sub.20, %                                                                             C.sub.30, %                                                                         C.sub.40, %                               ______________________________________                                        14         78.6     17.2      65.1  14.3                                      25         78.9     27.0      61.3  9.8                                       36         70.8     43.6      51.6  4.6                                       44         56.3     51.5      44.5  3.6                                       ______________________________________                                    

EXAMPLE 6

The effect of variations in the moisture content of the feed 1-decenewas studied in a series of experiments. The catalyst used in Example 5was also used in these experiments and all other reaction conditionswere the same except as shown in Table VI which sets out the results ofthese experiments.

                  TABLE VI                                                        ______________________________________                                                         Selectivity                                                  H.sub.2 O, ppm.                                                                       Temp. °C.                                                                        Conv. %  C.sub.20, %                                                                         C.sub.30, %                                                                         C.sub.40, %                            ______________________________________                                        12      27        60.3     33.5  59.8  6.0                                    27      14        79.8     26.6  63.6  9.3                                    42      27        79.3     27.3  61.3  9.6                                    80      27        82.4     31.6  60.1  7.3                                    ______________________________________                                    

EXAMPLE 7

A series of experiments was carried out to study the effect onconversion and product selectivity resulting from variations in the flowrate of the 1-decene through the catalyst. The same catalyst as used inExample 2 was used in these experiments subsequent to this earlierexperiment. In these experiments the flow rates of the 1-decene and theboron trifluoride injection rates were periodically increased to providea constant 3.08 weight percent amount of boron trifluoride in the1-decene in each experiment. The hot spot temperature rose as the feedrate increased as a result of the higher heat generation at increasingfeed rates and constant conversion. The results are set out in TableVII.

                  TABLE VII                                                       ______________________________________                                        1-decene,                                                                            Temp.             Selectivity                                          cc/hr. °C.                                                                             Conv. %  C.sub.20, %                                                                           C.sub.30, %                                                                         C.sub.40, %                            ______________________________________                                         60    26       84.9     38.3    54.6  7.1                                    150    31       84.1     29.9    58.4  10.0                                   240    39       85.9     36.0    55.5  7.5                                    ______________________________________                                    

In the above table the flow of 1-decene was a liquid hourly spacevelocity of about one per hour at the start and was increased to aboutfour per hour at the completion for the final experiment.

EXAMPLE 8

This example demonstrated the high activity of a catalyst after 257hours of reaction time. The catalyst was used over a large number ofexperiments at many different reaction conditions including a cycle ofexperiments using pure 1-decene feed followed by a cycle of experimentsusing a feed stream comprising 1-decene with a dimer fraction. Theamount of water in the feed varied from a low of 12 ppm. to a high of 80ppm. over the series of experiments. The solid adsorbent was 30 cc. of a20/30 mesh (0.59 to 0.84 mm.) silica.

In the last experiment which used pure 1-decene the 1-decene containing80 ppm. water was fed to the reactor at a rate of 90 cc. per hour andthe boron trifluoride was fed at a rate of 12.0 cc. per minute. Thereactor was operated at an outlet pressure of 125 psig. (0.965 MPa).After seven hours of this experiment, which was a total of 148 hours useof the catalyst, at which time the hot spot temperature was 27° C.,analysis of the product showed a conversion of 82.4 percent at aselectivity of 31.6 percent to the dimer, 60.1 percent to the trimer and7.3 percent to the tetramer.

The feed was then switched to a mixture comprising the pure 1-decene anda monomer-dimer product fraction which analyzed 39.9 percent 10-carbonolefin, 15.4 percent 10-carbon paraffin, 43.8 percent dimer and 0.9percent trimer. In the last experiment an amount of the monomer-dimerproduct was added to the pure 1-decene to provide a feed streamcontaining 17 percent dimer. In this final experiment this feed streamwhich also contained 32 ppm. water was introduced into the reactor at arate of 30 cc. per hour and the boron trifluoride was fed at the rate of12.0 cc. per minute. The reactor was operated at an outlet pressure of125 psig. (0.965 MPa). After 13 hours of this experiment, which was atotal of 257 hours use of the catalyst, at which time the hot spottemperature was 16° C., product analysis showed a conversion of 81.5percent at a selectivity of 19 percent to the dimer, 63.3 percent to thetrimer and 17.4 percent to the tetramer.

EXAMPLE 9

In a further series of runs a 30 cc. sample of a 10/20 mesh (0.84 to 2.0mm.) silica was used as the solid adsorbent. In one experiment 70 cc. ofa feed comprising 1-decene, a sufficient amount of the monomer-dimerfraction described in Example 8 to provide 15 percent dimer and 26 ppm.water was introduced into the reactor at a rate of 70 cc. per hour. Theboron trifluoride was fed at a rate of 3.10 cc. per minute, which wasone percent boron trifluoride in the feed mixture. The hot spottemperature was 11° C. and the outlet pressure was 100 psig. (0.793MPa). Analysis of the product after four hours at these operatingconditions showed a conversion of 85.4 percent at a selectivity of 23.3percent to dimer, 61.4 percent to trimer and 14.7 percent to tetramer.

EXAMPLE 10

Example 9 was repeated at the same conditions except that the 1-olefinfeed rate was 73 cc. per hour and the water content of the feed was 37ppm. The significant difference was a reduction in the feed rate of theboron trifluoride down to a rate of 1.50 cc. per minute, which was 0.49percent of the 1-olefin mixture fed to the reactor. After two hours ofoperation, analysis of the product showed a drop in the conversion downto 67.6 percent at a selectivity of 18.7 percent to the dimer, 67.1percent to the trimer and 11.7 to the tetramer. Further analysis afteroperating an additional hour showed that the conversion had furtherdropped to 50.5 percent without much change in the selectivity.

A comparison of Examples 9 and 10 reveals that at the particularoperating conditions used in these experiments one percent borontrifluoride in the feed was sufficient while 0.49 percent wasinsufficient.

EXAMPLE 11

The series of experiments using the solid adsorbent described inExamples 9 and 10 was concluded by a final experiment which itself wasconducted for 57 hours. This experiment was carried out using a feedrate of 75 cc. per hour of the same feed mixture containing 15 percentdimer and 25 ppm. water. The feed rate of the boron trifluoride was 2.70cc. per minute which amounted to 0.87 percent boron trifluoride in thefeed mixture. The reactor was operated at an outlet pressure of 100psig. (0.793 MPa) and a hot spot temperature of 18° C. Analysis of theproduct at the end of this experiment, which represented about 400 hoursof use of this catalyst over a period of three weeks, showed aconversion of 82.9 percent at a selectivity of 20.4 percent to dimer,64.1 percent to trimer and 14.9 percent to tetramer.

This final experiment demonstrated that a boron trifluorideconcentration as low as 0.87 weight percent in the feed and a moisturelevel as low as 25 ppm. was adequate to obtain superior agingcharacteristics and stability. It was further observed that the hot spotremained at the entrance of the silica bed for the entire 57 hours ofthe experiment, which indicated that most of the conversion took placeat the inlet of the catalyst bed and that there was, therefore, no signsof aging.

It is to be understood that the above disclosure is by way of specificexample and that numerous modifications and variations are available tothose of ordinary skill in the art without departing from the truespirit and scope of the invention.

We claim:
 1. The process for oligomerizing an alpha-olefin having fromthree to twelve carbon atoms and mixtures thereof with a heterogeneouscatalyst which comprises contacting said alpha-olefin in a reactor at atemperature between about -50° and about 150° C. with a three-componentsolid catalyst comprising a solid adsorbent in particulate form having aboron trifluoride and water adsorbed thereon.
 2. The process foroligomerizing an alpha-olefin in accordance with claim 1 in which astream of the alpha-olefin is introduced into the reactor and contactedwith the said three-component solid catalyst and a product stream isremoved from the reactor.
 3. The process for oligomerizing analpha-olefin in accordance with claim 2 in which the solid adsorbentcomprises from about 50 to 100 percent silica.
 4. The process foroligomerizing an alpha-olefin in accordance with claim 2 in which apartial pressure of boron trifluoride of between about atmospheric andabout 1,000 psig. (7.03 MPa) is maintained in the reactor.
 5. Theprocess for oligomerizing an alpha-olefin in accordance with claim 2 inwhich the partial pressure of boron trifluoride in the reactor isbetween about 50 and about 500 psig. (about 0.44 and about 3.55 MPa). 6.The process for oligomerizing an alpha-olefin in accordance with claim 2in which the temperature is between about -10° and about 50° C.
 7. Theprocess for oligomerizing an alpha-olefin in accordance with claim 2 inwhich the alpha-olefin comprises 1-decene.
 8. The process foroligomerizing an alpha-olefin in accordance with claim 2 in which thewater content of the alpha-olefin feed is between about 5 and about 130ppm.
 9. The process for oligomerizing an alpha-olefin in accordance withclaim 2 in which the alpha-olefin is flowed through the reactor incontact with a bed of the three-component solid catalyst at a liquidhourly space velocity between about 0.1 and about 50 hour⁻¹.
 10. Theprocess for oligomerizing an alpha-olefin in accordance with claim 2 inwhich the solid adsorbent has a particle size between about 10 and about50 mesh (about 0.3 and about 2.0 mm.).
 11. The process for oligomerizing1-decene to a product predominant in the trimer of 1-decene whichcomprises contacting a stream of 1-decene containing from about 5 toabout 130 ppm. water and a stream of boron trifluoride with a catalystcomprising particulate silica at a temperature of between about -10° andabout 50° C. under a partial pressure of boron trifluoride between about10 and about 500 psig. (about 0.17 and about 3.55 MPa).
 12. A method ofregenerating a deactivated solid catalyst comprising boron trifluorideadsorbed on a solid adsorbent which has been deactivated in theoligomerization of an alpha-olefin, the step which comprises contactingsaid deactivated solid catalyst with a stream comprising a liquidalpha-olefin containing dissolved water.
 13. A method of regenerating adeactivated solid catalyst comprising boron trifluoride adsorbed on asolid adsorbent in accordance with claim 12 in which the solid adsorbentis silica.